> On Oct 16, 2019, at 1:00 AM, Yufen Yu <yuyufen@xxxxxxxxxx> wrote:
>
> We have a test case as follow:
>
> mdadm -CR /dev/md1 -l 1 -n 4 /dev/sd[a-d] \
> --assume-clean --bitmap=internal
> mdadm -S /dev/md1
> mdadm -A /dev/md1 /dev/sd[b-c] --run --force
>
> mdadm --zero /dev/sda
> mdadm /dev/md1 -a /dev/sda
>
> echo offline > /sys/block/sdc/device/state
> echo offline > /sys/block/sdb/device/state
> sleep 5
> mdadm -S /dev/md1
>
> echo running > /sys/block/sdb/device/state
> echo running > /sys/block/sdc/device/state
> mdadm -A /dev/md1 /dev/sd[a-c] --run --force
>
> When we readd /dev/sda to the array, it started to do recovery.
> After offline the other two disks in md1, the recovery have
> been interrupted and superblock update info cannot be written
> to the offline disks. While the spare disk (/dev/sda) can continue
> to update superblock info.
>
> After stopping the array and assemble it, we found the array
> run fail, with the follow kernel message:
>
> [ 172.986064] md: kicking non-fresh sdb from array!
> [ 173.004210] md: kicking non-fresh sdc from array!
> [ 173.022383] md/raid1:md1: active with 0 out of 4 mirrors
> [ 173.022406] md1: failed to create bitmap (-5)
> [ 173.023466] md: md1 stopped.
>
> Since both sdb and sdc have the value of 'sb->events' smaller than
> that in sda, they have been kicked from the array. However, the only
> remained disk sda is in 'spare' state before stop and it cannot be
> added to conf->mirrors[] array. In the end, raid array assemble
> and run fail.
>
> In fact, we can use the older disk sdb or sdc to assemble the array.
> That means we should not choose the 'spare' disk as the fresh disk in
> analyze_sbs().
>
> To fix the problem, we do not compare superblock events when it is
> a spare disk, as same as validate_super.
>
> Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
Please add "---" before "v1->v2:". etc. This will hint git to not
include these change lists during git-am.
>
> v1->v2:
> fix wrong return value in super_90_load
> v2->v3:
> adjust the patch format to avoid scripts/checkpatch.pl warning
> v3->v4:
> fix the bug pointed out by Song, when the spare disk is the first
> device for load_super
> ---
> drivers/md/md.c | 57 +++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 51 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 1be7abeb24fd..fc6ae8276a92 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1149,7 +1149,15 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
> rdev->desc_nr = sb->this_disk.number;
>
> if (!refdev) {
> - ret = 1;
> + /*
> + * Insist on good event counter while assembling, except
> + * for spares (which don't need an event count)
> + */
> + if (sb->disks[rdev->desc_nr].state & (
> + (1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE)))
> + ret = 1;
> + else
> + ret = 0;
Have you tried only passing a couple spare disks to mdadm -A? I guess
we will end up with freshest == NULL in analyze_sbs(), which will
crash in validate_super().
Thanks,
Song
